Heating hydrocarbon fluids



Oct. 1, 1940. I H, v, T LL 2,216,684

HEATING HYDROCARBON FLUIDS Filed April 1, 1938 PIC-3.1. 38 f INVENTOR #40040 KAIWELL ATTORNEY ism/r10 Man/R:

Patented Oct. 1, 1940 PATENT OFFICE- HEATING HYDROOARBO'N FLUIDS HaroldV. Atwell, White Plains, N. Y., assignor to Gasoline Products Company, Inc, Newark, N; J a corporation of Delaware Application April 1, 1938, Serial N0. 199,358

8 Claims.

This invention relates to methods of and apparatus for heating fluids, more particularly for heating hydrocarbon fluids to conversion temperatures.

According to my invention a furnace is provided having combustion tubes adjacent heater tubes adapted to convey hydrocarbons to be heated. Each combustion tube is provided with a diffusion burner to which the fuel and air are 10 supplied as separate streams or layers and substantially no turbulence is obtained during combustion. In this way combustion is delayed by slow diffusion between thestreams or layers of fuel and air passing through the combustion 5 tube and a relatively uniform temperature is maintained throughout the length of the combustion tube. By the slow diffusion an elongated flame is obtained and the entire combustion tube is heated to a relatively high uniform tempera- 20 ture throughout its length and each combustion tube forms a source of radiant heat. The com-' bustion tubes may be made of metallic or nonmetallic refractory material.

Aplurality of combustion tubes is arranged in 25 the furnace and a plurality of heater tubes is placed in the furnace around the combustion tubes. As the flames are entirely confined in the combustion tubes, the heater tubes may be placed close to the combustion tubes and a very compact 30 furnace is obtained. The combustiontubes may be arranged in horizontal or-vertical planes and the heater tubes may also be arranged in horizontal or vertical planes. Or the combustion tubesmay be arranged in horizontal planes and I 35 the heater tubes in vertical planes or vice versa.

Any arrangement of the tubes may be used.

The combustion tubes are used as a source of radiant heat and the heater tubes are so arranged with respect to the combustion tubes that certain 40 of the heater tubes are preferably heated on both sides by radiant heat whereby the hydrocarbons passing through such heater tubes are rapidly raised to a relatively high temperature. The firing of the burners is capable of exact control so 45 that it is possible to maintain any desired temperature in a selected combustion tube.

The hot combustion gases from the combustion tubes pass to a common flue which may be provided with a bank of tubes for preheating the hy- 50 drocarbons which are to be passed through the heater tubes adjacent the combustion tubes. Or the hydrocarbons may be preheated in other ways and the bank of tubes in the flue may be used as a soaker section. The hydrocarbons preheated 55 in any suitable manner are passed through the heater tubes eitherin a series flow or in parallel streams, preferably in series flow and are subjected to radiant heat to raise the hydrocarbons to a conversion temperature. The hydrocarbons. are then passed through a soaking section where- 6 in they are maintained at a conversion-temperature for the desired time. If desired, the furnace may be provided with a separately fired soaking section, or a separate soaking section may be used. The products of conversionare then treat- 10 ed in any Well known manner to separate light hydrocarbons containing gasoline I constituents.

In the drawing, I have diagrammatically illus-' trated one form of-ap-paratus adapted for practicing my invention in which:

Fig. 1 represents a transverse vertical cross section of a furnace;

Fig. 2 represents a partial longitudinal cross section taken substantially on line 2-2 of Fig. 1 and showing the stack, parts being omitted to facilitate the disclosure;

Fig. 3 represents an enlargedcross section taken through the inlet end of a combustion tube; and

Fig. 4 represents an enlarged cross section taken through the outlet end of the combustion tube shown in Fig. 3.

Referringnow to the drawing, the reference character l0 designates a furnace provided with a heating section l2 and a soaking section M. The heating section is heated by a plurality of horizontally extending combustiontubes arranged in vertical rows l6 and I8. Surrounding the comv bustion tubes are interconnected heater tubes adapted to convey hydrocarbon fluids to be heated. Certain of the heater tubes are heated on one side by direct radiation from the combustion tubes and on the other by reradiation from the furnace walls. These heater tubes comprise a top row 20, a side row 22 adjacent side wall 23 of the furnace, bottom row 24 and vertical row 26 adjacent side wall 21 of the furnace. The remaining heater tubes 30 are so arranged with respect to the combustion tubes l6 and I8 that they are heated on both sides by radiant heat generated within the combustion tubes l6 and I8. The combustion tubes l6 and. I8 may be made of metallic or non-metallicrefractory material. For example, carborundum tubes or chromium steel tubes may be used. As shown in the drawing the combustion tubes preferably have a larger diameter than the heater tubes. Arrangements of tubes other thanthat shown in Fig. 1 may be used where radiantheat from the combustion tubes is used to provide heat for the heater tubes.

While I prefer to use a combustion tube circular in cross section, other shapes may be used.

The hydrocarbon fluids after being heated to a conversion temperature in the heater tubes in heating section [2 of the furnace, pass through heater tubes 32 which surround combustion tube 34 positioned in the soaking section M of the furnace wherein they are maintained at a conversion temperature for. the desiredtime. After leaving the soaking section, the conversion products are further treated to separate the desired hydrocarbons therefrom. Hydrocarbon fluids to be heated in the heater tubes are. passed through line 36 by pump 38, through the heater tubes which are positioned between the combustion tubes l6 and I8 and then through the bottom, top and side rows of the heater tube s. The heated hydrocarbon fluids are then passed through tubes 32 in the soaking section l4 and then leave through line 40.

The combustion tubes l6 and 18 are used as the source of radiant heat for. heating the heater tubes. The combustion tubes I'Ei'and H) are heated in such a manner as to maintain each combustion tube at a substantially uniform temperature throughout its length. This effect is obtained by carrying out the combustion in a way to produce a long fiame in each combustion tube. In other words, the combustion between the fuel and the air is delayed so that it takes place during the passage of the fuel and the air through the combustion tube and an elongated flame is obtained which heats the entirelength of the combustion tube. Each combustion tube is preferably provided with a burner. While the comprovided with a valved inlet 4a. .Air for the combustion of the fuel admitted through line 44 is drawn into the combustion tube l6 around the tube 46 as at "50. In this type of burner the I fuel and air are not mixed prior to the burning but it is desirable to maintain the fuel and air separate in layers so that diffusion will take place between the layers and slow combustion will result. In this way an elongated flame is obtained which heats the combustion tube throughout its length and maintains it at substantially the same temperature throughout. When the burner is to be set into operation an ignition mixture is passed through line 48 and burned as it passes through the tube 46 in order to ignite the fuel introduced into the combustion tube I 6 through line 44. If desired, the ignition mixture may be passed through line 48 during the combustionin the tube IS in order to'insure proper burning of the fuel introduoedthereinto.

Air which is admitted through opening 50 is not forced into-the open end of the combustion tube I6 under pressure but is drawn into the tube l6 by the Venturi tube construction generally designated as 52 which is positioned at the other end of the combustion tube -l6.' This construc-. tion includes a valved line 56provided with a jet orifice nozzle 51 which discharges fluid such as air into the Venturi tube 54 to create suction which draws in the desired amount of air into the combustion tube l6. Each combustion tube has a Venturi tube construction as shown and de scribed in connection with combustion tube l6. By varying the quantity of fluid introduced through line 55 and by varying the fuel introduced through line 44 different temperatures may be obtained in the combustion tubes [6 and I8 and this forms a means for controlling the temperature of each combustion tube.

The combustion gases leaving through the Venturi constructions 52 pass through line 58, through a heating section 59 to a stack and then to the atmosphere. The combustion gases pass over the heater or preheating tubes 62 which are positionedin. heating section 59. The portion of a line 56 shown below the line 58 is the exhaust line leading from another of the combustion tubes. The exhausts from the combustion tubes are so arranged that they all discharge into the heating section 59 below the stack 653 "and in this way substantially all of the heat in the waste gases is used to. heat or preheat hydrocarbon fluids passing through heater tubes 62. If the heater tubes 62 are used as preheater tubes, the hydrocarbon fluids after being passed'therethrough leave through line 68 and are passed through line 36 and further heated in the heater tubesin the heating section 12 and the soaker section l4 of the furnace 10. If desired, the heater section 59 may be omitted. Or the soaker section l4 may be omitted and the heater section '59 used as a soaker section. While I have shown lines 58 and 66 as directing gases "of combustion onto the heater tubes 62, it is to be'understood that the lines 58, 66 and others not shown, extending from the combustion tubes [6 and I8 may be arranged so that all the hot products-of combustion from the combustion tubes are introduced into the heating section 59 beneath the tubes 62 therein so that all the'hot products of' combustion will move upwardly'through heating section 59 and past all the tubes 62 and thento the stack 60.

One method of treatinghydrocarbons according to my invention will now be given but it is to be understood-"that I am not restricted'thereto as many variations and modifications are possible and also other hydrocarbon fluids may be treated using the principles of my invention. An oil stock to be cracked such as a gas oil stock is passed through heater'tubes 62 inthe heating section '59 where it" is heated by the hot products of combustion from the combustion tubes to about 650 to 750 F. The oil stock to be cracked s maintained under a superatmospheric pressure of about 200 to 1000 pounds per square inch during its passage through the heater tubes. Pressures from atmospheric to about 3000 pounds per square inch may be used. The preheated oil stock is then passed through the heater tubes 30 which are positioned between combustion tubes l5 and. I8 in the heating section l2 of the furnace I!) and the oil has its temperature rapidly raised... These heater tubes. 30 are so arranged with-respect to the combustion tubes l6 and I8 that they are'heated on both sides by radiant heat generated within the combustion tubes l6 and l8; 1 v

Fuellsuch as gas is burned in the combustion tubes I 6 and I8 by'a delayed combustion as above described whereby the combustion tubes are substantially uniformly heated to a relatively high temperature. The combustion tubes form a source of radiant-heat for heating the heater tub'es'and 'oil passing through the heater tubes.

The walls of the furnace are also heated by the heat from the combustion tubes and the heated walls reradiate heat to the sides of the heater tubes not heated by radiant heat from the combustion tubes. By the slow combustion an elongated flame is maintained within each of the combustion tubes to heat the combustion tube along its entire length to substantially the same temperature. Different combustion tubes may be fired diflerently so that the combustion tubes may beat different temperatures Where it is desired to vary the heat'input' to heater tubes and the hydrocarbon fluid passing therethrough in different sections of the furnace. It is only necessary to maintain each combustion tube at a substantially uniform temperature so that the hydrocarbon fluids passing through the heater tubes are heated uniformly.

By heating the combustion tubes 16 and I8 to a uniform temperature, the heater tubes surrounding them and the hydrocarbon fluids passing throu h the heater tubes are uniformly heated. After passing through the heater tubes 30 the oil is passed through the bottom row of tubes 2 vertical row of tubes 22. top row of tubes 1!!! and vertical row of tubes 26 of the heater tubes wherein it has its temperature raised to about 900-1050" F.. preferably about 950-975 F. The heated oil is then passed through tubes 32 which surround combustion tube 34 in the soaking section 14. The combustion tube 34 is heated bv delaved combustion the same as tubes [6 and i8 but the temperature is maintained lower so that while heat is added to the oil undergoing conversion. the temperature of the oil passing through the soaker section preferably does not rise substantially above the desired maximum temperature. preferably about 975 F. Instead of using gas oil stock and converting it into lower boiling hydrocarbons, my invention may also be used to treat normally gaseous hydrocarbonfluids in order to convert them into higher boiling hydrocarbon constituents containing gasoline. For example. temperatures of 750 to 1750 F. may be used where other hydrocarbon fluids are to be treated.

While I have set forth one example of a method of practicing my invention it is to be understood that this is by way of illustration only and various changes and modifications may be made in' the method and apparatus disclosed herein without digressing from the spirit of my invention.

I claim:

1. A process for raising hydrocarbon fluids to conversion temperature which comprises passing hydrocarbon fluid through heater tubes arranged in a chamber to surround separately fired combustion tubes therein, burning fuel throughout substantially the entire length of each of said combustion tubes so that a long flame is produced and each combustion tube is heated uniformly to a high temperature and forms a source of radiant heat, transmitting radiant heat from said combustion tubes to said heater tubes and the hydrocarbon fluid passing through said heater tubes so that the hydrocarbon fluid is heated substantially uniformly during its passage through said heater tubes.

2. A process for raising hydrocarbon fluids to a relatively high temperature which comprises passing hydrocarbon fluid through heatertubes arranged in a chamber to surround a combustion tube therein, burning gas throughout substantially the entire length of said combustion tube so that a long flame is produced and the combustion tube-is heated uniformly to a high temperature and forms a source of radiant heat, transmitting radiant heat from said combustion tube to said heater tubes and the hydrocarbon fluid passing through said heater tubes so that the hydrocarbon fluid is heated substantially uni-' formly'during its passage through said heater tubes and is raised to a conversion temperature and then passing the heated hydrocarbon fluid through other heater tubes surrounding another combustion tube wherein it is further heated and is maintained at a-conversion temperature.

3. A process for raising hydrocarbon fluids to conversion temperatures which comprises passing hydrocarbon fluid through heater tubes arranged between combustion tubes substantially uniformly heated throughout their lengths so that saidheater tubes receive radiant heat on both sides thereof to rapidly raise the tempera ture of the hydrocarbon fluid passing through said heater tubes, then passing the heated hydrocarbon fluid through other heater tubes so arranged with respect to said combustion tubes that said last mentioned heater tubes receive radiant heat from said combustion tubes on one side only to further heat the hydrocarbon fluid passing through said last mentioned heater tubes.

4. A furnace adapted to raise hydrocarbon fluids to conversion temperatures including a heating section provided with a plurality of heater tubes adapted to convey hydrocarbon fluids to be heated and a plurality of separateand spaced combustion tubes each surrounded by said heater tubes and adapted to supply radiant heat to said heater tubes and the hydrocarbon fluids passing therethrough, each of said combustion tubes being adapted to be maintained at a substantially uniform temperature throughout its length whereby said heater tubes are substantially uniformly heated by heat emanating from said combustion tubes.

5. A heater adapted to raise hydrocarbon fluids to relatively high temperatures including a heating section provided with a plurality of heater tubes adapted to convey hydrocarbon fluids to be heated, a plurality of separate and spaced combustion tubes each surrounded by said heater tubes, meansfor burning fuel within each of said combustion tubes .to raise said combustion tubes to a relatively high temperature and for maintaining each of said combustion tubes at a desired substantially uniform temperature throughout its length whereby each combustion tube is a source of radiant heat and said heater tubes are substantially uniformly heated by radiant heat.

6. A heater adapted to raise hydrocarbon fluids to relatively high temperatures including a heating section provided with a plurality of heater tubes adapted to convey hydrocarbon fluids to be heated, a plurality of combustion tubes, each combustion tube being surrounded by said heater tubes, means for burning fuel within said combustion tubes to raise said combustion tubes to a relatively high temperature and for maintaining each of said combustion tubes at a substantially uniform temperature throughout its length whereby each combustion tube is a source of radiant heat, certain of said heater tubes being arranged between adjacent combustion tubes whereby said heater tubes receive radiant heat on both sides thereof from said combustion tubes.

7. A heater adapted to raise hydrocarbon fluids to relatively high temperatures including a heating section provided with a plurality of heater tubes adapted to convey hydrocarbon fiuids to be heated, a plurality of separate and spaced combustion tubes each surrounded by said heater tubes, means for burning fuel within said combustion tubes to raise said combustion tubes to a relatively high temperature and for maintainme each of said combustion tubes at a substantially uniform temperature throughout its length whereby each combustion tube is a source of radiant heat, certain of said heater tubes receiving radiant heat on one side only from said combustion tubes, and a soaker section provided with heater tubes and a combustion tube, said last mentioned heater tubes being adapted to convey heated hydrocarbon fluids leaving the heating section of the furnace, and means for maintaining said last mentioned combustion tube at a uniform temperature throughout its length sothat the hydrocarbon fluids passing through said heater tubes in said soaker section are maintain'ed at a substantially uniform conversion temperature.

8. A heater adapted to raise hydrocarbon fluids to relatively high temperatures including a heatingsection provided with a plurality of heater tubes adapted to convey hydrocarbon fluids to be heated, a plurality of separate and spaced combustion tubes each surrounded by said heater tubes, means for burning fuel within said combustion tubes to raise said combustion tubes to a relatively high temperature and for maintaining eachof said combustionjubes at a substantially uniform temperature'through its length whereby each combustion tube is a source of radiant heat, a soaker section provided with heater -tubes. adapted to convey hydrocarbon fluids after being heated in said heating section and separate means for heating said soaker section. I

HAROLD V. ATWELL. 

